The present invention relates to an inflator for filling up an air bag for a motor vehicle or an inflatable article, and more particularly to an initiator (an electric trigger device) assembly for igniting a propellant (that is, a gas generating agent) in an inflator.
An initiator for inflating an air bag of a motor vehicle or the other expansible article includes an initiator assembly for igniting a propellant (a gas generating agent) stored in a housing of an inflator. The inflator activates the propellant (the gas generating agent) with activation of the initiator assembly so as to generate a gas for filling the inflatable article. The initiator assembly generally has an outer shape or includes a member for being connected to a supporting structure (for example, a structure in an inner tube of the inflator).
Conventionally, there has been known an initiator having an outer metal casing with a boss or a collar for connecting to an inflator housing. The collar is positioned on an outer periphery of an insulating material surrounding a conductive pin of the initiator. Further, in a design of another known initiator assembly, there has been known a cover having an injection-molded portion made of a plastic material surrounding an initiator. Such an initiator assembly is disclosed, for example, in JP-A 9-506965 and JP-A No. 11-321541.
In JP-A 9-506965, there is disclosed an initiator assembly in which a casing is made of a metal wall mounted to an metal end plate, and is provided with a molded product made of a plastic material so as to be formed in such a manner as to surround an end plate and a part of an electrode inserted to the end plate.
Further, in JP-A No. 11-321541, there is disclosed an initiator assembly having an inserted member which is injection-molded with an insulating material to be unified and being characterized by a shoulder portion having a comparatively short length and engaging with a trigger device adapter.
However, it is desired to make it further easier to connect the initiator assembly to the inflator housing as well as reducing a size of the injection-molded portion of the plastic material. However, it is impermissible that such the initiator aspect applies a further load to production of the initiator assembly and increases a manufacturing cost of the initiator assembly.
The present invention is made so as to solve the problems mentioned above, and an object of the present invention is to provide an initiator assembly which can be easily manufactured without increasing a cost, and can be easily and securely connected to a connector at a time of being used.
In accordance with the present invention, there can be provided an initiator assembly in which an inflator is improved. The initiator assembly ignites and burns a priming arranged close to a conductive pin of the initiator when it is activated with an igniting signal received by the conductive pin. The initiator assembly includes an initiator and a collar assembly joined to the initiator. In addition to at least one conductive pin, the initiator can have a cap member (a charge holder) made of a metal wall surrounding the priming to be ignited when the igniting signal is received. The collar assembly holds the initiator with respect to a housing of the inflator even after being activated.
The initiator assembly according to the present invention corresponds to an initiator assembly in which an initiator used for igniting a priming and having at least one conductive pin and a metal collar for holding the initiator assembly with respect to an inflator are integrally formed by an insulating material injection-molded between both members. In the case of employing a plastic material capable of being injection-molded as an insulating material, the injection-molded plastic material is solidified so as to form a molded resin portion, which connects integrally the initiator with the metal collar. In other words, the initiator, the metal collar and the insulating material existing between both members are simultaneously integrated due to the injection-molding of the insulating material so as to form the initiator assembly. In this case, in the present specification, for convenience of explanation, a combination of the injection-molded insulating material and the metal collar is referred as a collar assembly, and a combination of the collar assembly and the initiator is referred as an initiator assembly.
The collar assembly includes the injection-molded insulating material (hereinafter, also refer to as an insulating material in the same meaning) and the metal collar, and the metal collar is fixed and joined to the insulating material made of the injection-molded plastic material during an injection-molding process. The insulating material is useful for insulating one conductive pin from a second conductive pin, or in another aspect, the insulating material is useful for insulating one conductive pin from another conductive component in a different electric potential when the one conductive pin receives the igniting signal. The metal collar is a single integral piece and can be defined as one including a body portion and a shoulder portion. In the body portion, a front end annular cylindrical body portion thereof is arranged to be fitted and fixed to an outer periphery of the insulating material made of a molding plastic which is injection-molded to surround two conductive pins normally comprising a center pin and a grounding pin, the conductive pin extends into a cylindrical body portion (that is, a rear half portion) extending rearward, and a connector connected to the conductive pin is received in the inner space of the rear cylindrical body. In this metal collar, it is desirable that the rearward extending cylindrical body portion is formed so that the inner periphery thereof is not covered with an insulating material (that is, an injection-molded resin or the like) and the metal collar is exposed. This is for unfailingly preventing a connector arranged in the inner space of the circular portion from dropping out due to an impact at a time of activation of the initiator or the like.
The shoulder portion can be formed at a position at which the metal collar is separated into substantially a front half portion and a rear half portion, and is protruded outwardly in the radial direction from the body portion so as to be contacted and engaged with an engaging portion of the inflator housing. A mutual engagement between the shoulder portion and the engaging portion of the inflator housing controls a relative positioning of the initiator assembly with respect to the inflator housing before and after activating the initiator assembly. The outward position of the shoulder portion defines an outer length or size of the metal collar.
The initiator assembly according to the present invention can be formed, for example, as a structure in which the priming is stored in the charge holder composed of a cylindrical metal wall mounted to a metal eyelet (an end plate), the metal eyelet has a perforated cylindrical shape and a central hole is filled with an electric insulating body (normally made of a glass). In this case, the center pin of the electrode goes through the insulating material in the metal collar, continuously goes through the electric insulating body in the eyelet, and a front end thereof is connected to the priming. Further, the upper surface of the eyelet is in contact with the priming, and the second conductive pin, that is, a front end of the grounding pin of the electrode is connected to the lower surface of the eyelet in a state capable of turning on electricity. As the priming stored in the charge holder, a zirconium-potassium perchlorate material can be used. Further, the means for triggering the priming upon the igniting signal is provided between the center pin and the eyelet. That is, it is constituted by a resistance line connected between members.
The initiator assembly according to the present invention can accompany with the following features.
(1) A projection is formed on an outer peripheral surface of the insulating material (the molding resin portion) surrounding the metal eyelet (the end plate) in order to increase a friction between the inner tube of the inflator and the initiator assembly and to prevent the initiator assembly from being shaky and rotating, thereby facilitating a crimping process of the inner tube. It is desirable that the projection is formed in various kinds of conical shapes such as a circular cone, a rectangular cone, however, may be formed in the other shapes, for example, in a belt-like shape along the circumferential direction, that is, can be optionally formed in a shape as far as being fitted between the inner tube and the initiator assembly and capable of increasing a frictional resistance. Further, this projection is formed to be slightly larger than a gap obtained between the inner tube and the initiator assembly, and is formed so as to press-insert the initiator assembly to the gap between the initiator assembly and the inner tube by being crushed or bent at a time of joining the initiator assembly to one end of the inner tube. In order to obtain the function mentioned above, for example, in the case that the width of the gap is 0.75 mm, it is realized by making the projection about 0.1 to 0.2 mm larger than the gap.
(2) The connector in the metal collar and the center pin and the grounding pin in the connecting space are made such as not to be protruded from the collar for preventing the pin from being deformed during assembling the initiator assembly.
(3) A dislocation-preventing means of the connector is provided in the connecting space for the connector inside the metal collar. A recessed notch can be provided in the metal collar as the preventing means.
(4) The inner side of the metal collar is not covered by the injection-molded insulating material (the molding plastic material), and the connector is fitted to the metal surface within the collar so as to be directly brought into contact therewith. Accordingly, it is possible to prevent the connector from being taken out due to a reaction at a time of operating the initiator.
(5) A mounting means of the connector with a lead wire is provided so as to decide a particular direction of the lead wire with respect to the inflator. In particular, a recess or a projection extending in the axial direction is provided in an edge portion of the metal collar in an unsymmetrical way.
In accordance with the present invention, the initiator assembly which can be easily connected to the inflator housing is provided. Mutual connection between the inflator housing, the connector and the initiator assembly can be achieved, and the connector cannot be dislocated at a time of activation. In the present invention, the injection-molding of the insulating material, that is, the molding plastic material (the molding resin) in the metal collar promotes an assembling process of the initiator assembly. In particular, the metal collar is integrally fitted to the outer periphery of the plastic molded body, and the electrode pin of the initiator assembly is connected unfailingly to the connector without having the insulating material inside the portion for connecting the connector and without dislocation at the time of activation, which is achieved by the present invention for the first time.
Further, the respective end surfaces of the center pin, the eyelet and the electric insulating body are on the same plane, are integrally resin-molded, including the metal collar, and can be formed as a pin type. The pin type corresponds to the initiator having the conductive pin protruded into the inner space of the rear cylindrical body of the body portion in the collar assembly, particularly the metal collar, in which the conductive pin and the lead wire are connected to each other by receiving and engaging the connector at the front end of the lead wire with the inner space of the rear cylindrical body in the body portion, whereby the pin and the wire can be conductive. The pin type initiator mentioned above can make a overall size of the initiator compact and be easily treated by independently attaching the connector and the lead wire for electrifying afterwards. In the pin type initiator mentioned above, by arranging the respective end surfaces of the center pin, the eyelet and the insulating body on the same plane, the initiator assembly which can be easily manufactured and does not increase the cost can be realized. That is, it is possible to provide the electric resistance body (the resistance line in the present specification) converting the electric energy such as the electric signal into a thermal energy between the conductive pin and the conductive component linearly without being bent. That is, the resistance line can be simply and securely connected to the conductive pin and the conductive component.
As the insulating material injection-molded so as to surround a part of the initiator, the plastic material capable of being injection-molded can be used. It is possible to employ an engineering plastic, for example, nylon such as a nylon 6, a nylon 12, a nylon 6-12 and polyester such as a polybutylene terephthalate (PBT), a polyethylene terephthalate (PET). Further, in order to improve a mechanical strength, a glass fiber or the like can be contained in the insulating material.
The other advantages of the present invention can be easily understood from the following description with respect to preferred embodiments shown in the following drawings.
According to the present invention, such an initiator assembly can be realized as that connection to the inflator housing is performed easily, a size of the injection-molded portion (the resin portion) of the plastic material is reduced, and the load of work and the cost at manufacturing is not increased.
In particular, the initiator assembly according to the present invention can easily and securely connect the resistance line to the conductive pin and the conductive component since the respective end surfaces of the center pin, the eyelet and the insulating body are made in the same plane in the pin type initiator.